Power wrench for tightening studs in engine blocks and the like



Dec. 24, 1968 E. R. SHINN POWER WRENCH FOR TIGHTENING STUDS IN ENGINEBLOCKS AND THE LIKE Filed July 19, 1967 3 Sheets-Sheen 1 FIG. I

56 FIG. 5

H320 FIG. 6 4 4 FIG 7 INVENTOR ERNEST R.SH|NN By W A TT'Y R. S TIG 5 ANHIN TENIN D THE H G STUDS IN ENGINE LIKE E. FOR BLOCK Dec. 24, 1968POWER WRENCH Filed July 19, 1967 3 Sheets-Sheet 2 INVENTOR INN ATT Y IA; 4 Q

xix 4d v Dec. 24, 1968 E. R. SHINN 3,417,641

POWER WRENCH FOR TIGHTENING STUDS IN ENGINE BLOCKS AND THE LIKE FiledJuly 19. 1967 3 Sheets-Sheet 3 INVE/WOR ERNEST R. SHINN United StatesPatent 3,417,641 IGWER WRENCH FOR TIGHTENING STUDS IN ENGINE BLOCKS ANDTEE LIKE Ernest R. Shinn, Palos Park, 111., assignor of one-half toRobert M. Beucur, Oak Lawn, Ill. Filed July 19, 1967, Ser. No. 654,666 7Claims. (CI. 81-53) ABSTRACT OF THE DISCLOSURE A power wrench fordriving and tightening studs in engine blocks and the like. The wrenchbody has a shank suitable for mounting in a drill press chuck and asocket for telescopic reception over the stud to be tightened. As thestud bottoms in the socket of the continuously rotating wrench body, aseries of wedge elements are caused to move into wedging engagement withthe stud and, thereafter, the rotational movement of the wrench bodycauses the wedge elements to become self-energized against the stud withincreased wedging action so that the stud is turned in a tighteningdirection. Withdrawal of the wrench from the stud deenergizes the wedgeelements so that they release the stud.

The present invention relates to a power wrench for driving andtightening studs in the threaded holes or sock ets which are providedfor them in an engine block or the like.

Heretofore, it has been common practice in assembly line operation, aswell as in automobile repair shops, to effect the installation of thevarious studs which project vertically upwardly from the engine block ofan internal combustion engine for an automotive vehicle initially tothread the studs manually a slight distance into the thread ed holes inthe engine block and thereafter to tighten the studs with a Stillsontype wrench. This procedure is very awkward inasmuch as the largemultiplicity of closely arranged studs affords little freedom of wrenchmovement. The procedure also is time consuming not only by reason ofsuch lack of working space but also by reason of the fact that to insureequality of stud height in the completed engine block repeatedmeasurement of stud height during the stud-tightening operation must beresorted to. Stud removal or extraction operations are likewise hamperedby close stud proximity. Still further, application of a self-energizingjaw type wrench to the studs may damage the latter to such an extentthat difficulty is subsequently encountered in installing the cylinderhead on the engine block to which the studs have been applied.

The present invention is designed to overcome the above-noteddiificulties that are attendant upon the current method of studinstallation, and toward this end, it contemplates the provision of anovel power wrench in the form of a normally vertically extending,thimble-like casing having at the upper end thereof a shank portion bymeans of which it may be secured in or connected to the rotary chuck ofa conventional or standard drill press stand. The aforesaid casing ofthe improved wrench presents a socket for telescopic reception over agiven stud to be tightened and is possessed of certain internal movingparts including a multiple jaw clutch, the latter consisting of arelatively large number of generally radially disposed wedge plates,each of which establishes or constitutes a clutch jaw. Normally, thewedge plates are maintained out of clutching engagement with the studundergoing tightening but they are capable of being initially moved intoengagement with the stud at the time the stud enters the stud-receivingsocket in the wrench casing. Because the wrench is continuously rotated,as soon as the wedge plates move into clutching engagement with the studundergoing tightening, continued rotation of the wrench effects aself-energizing or binding action on the part of the wedge plates sothat the stud is firmly gripped "by the numerous surrounding wedgeplates and rotated in a tightening direction. A gauge on the drill pressstand indicates the proper depth of stud penetration into the engineblock or other work piece, and when this depth has been attained, thedrill press chuck, and consequently, the Wrench, is raised so that thestud becomes withdrawn from the socket. Initial raising of the wrenchterminates the self-energizing or binding action of the wedge plates SOthat clutch disengagement and consequent stud release is effected.

Since the wrench supporting chuck is continuously rotated, and since itis associated with a conventional drill press stand, it is merelynecessary to index the engine block or other Work piece to bring thevarious Studs successively into vertical register with the wrench,whereupon, as each stud is moved beneath the wrench, the operatinghandle of the drill press stand is manipulated to lower the rotatingchuck, and consequently, the wrench, upon the stud so that automaticstud tightening will take place. Upon raising of the chuck and wrench,the tightened stud is released and the engine block is indexed to bringthe next stud into position for stud-tightening purposes.

The provision of a stud-tightening wrench of the character brieflyoutlined above and possessing the stated advantages constitutes theprincipal object of the present invention.

The provision of a stud-tightening wrench which is extremely simple inits construction; a wrench which is possessed of operative mechanicalparts in the form of sheet metal stampings and, therefore, may bemanufactured at a low cost; a wrench which is rugged and durable and,therefore, will withstand rough usage; a wrench in which the variousparts are easily assembled and dismantled for purposes of inspection ofparts, replacement or repair thereof; a wrench which requires noadjustment to accommodate studs of varying height or diameter withincertain predetermined limits; a wrench which will not deface or damagethe studs to which it is applied; a wrench which will positively gripthe studs securely even when they are made of hardened steel; and awrench which otherwise is well-adapted to perform the services requiredof it, are further desirable features which have been borne in mind inthe production and development of the present invention.

Other objects and advantages of the invention not at this timeenumerated will readily become apparent as the nature of the inventionis better understood from a consideration of the following detaileddescription.

In the accompanying three sheets of drawings forming a part of thisspecification, one illustrative embodiment of the invention is shown.

In these drawings:

FIG. 1 is a fragmentary side elevational view showing a stud-tighteningWrench embodying the invention operatively installed in the rotary chuckof a drill 'press stand and in position over a stud preparatory totightening of the latter;

FIG. 2 is an enlarged partial sectional view taken vertically andcentrally through the wrench and on the line 22 of FIG. 1;

FIG. 3 is a horizontal or transverse sectional view taken on the line3-3 of FIG. 2;

FIG. 4 is a plan view of one of numerous clutch Wedge plates which areemployed in connection with the present invention;

FIG. 5 is an edge view of the clutch wedge plate of FIG. 4;

FIG. 6 is a plan view of one of two torque reaction clutch wedge plateswhich are employed in connection with the invention;

FIG. 7 is an edge view of the clutch wedge plate of FIG. 6;

FIG. 8 is an enlarged horizontal or transverse sectional view taken onthe line 88 of FIG. 2 and showing the clutch mechanism disengaged;

FIG. 9 is an enlarged sectional view similar to FIG. 8 but showing theclutch mechanism engaged on a stud to be tightened;

FIG. 10 is a perspective view of the slide member and a pair ofassociated drive elements which are employed in connection with thepresent invention, such view showing the positional relationship betweensaid slide member and associated drive elements;

FIG. 11 is a perspective View, similar to FIG. 10 but showing asubstitute slide member which, when incorporated in the wrench, willadapt the wrench for stud-removal operations; and

FIG. 12 is a horizontal or transverse sectional view taken on the line1212 of FIG. 2 and, in the interest of clarity, showing the clutch wedgeplates removed.

Referring now to the drawings in detail and in particular to FIG. 1, astud-tightening wrench embodying the principles of the present inventionis designed in its entirety by the reference numeral 10, such figurebeing a side elevational view so that only the outer wrench casing 12 isvisible. The casing 12 is generally of cylindrical configuration andincludes an enlarged body portion 14 from which there projects axially ashank portion 16. The latter is located at the upper end of casing 12and is adapted for retention in a suitable chuck such as the rotatablechuck 18 which forms a part of a conventional or standard drill pressstand (not shown). The casing 12 is provided with a knurled uppersection 19. The casing 12 also is provided with a deep axially extendingclutch-enclosing socket 20 (see FIG. 2) for telescopic reception overthe upper end of a stud S. The latter is shown in the drawings as beingloosely threaded socket 22 in the upper portion of an automotive engineblock 24. Preferably, in a commercially feasible installation, the drillpress stand will be stationary while the engine block 24 will besuitably mounted on a bed plate (not shown) which is capable of beingindexed to bring the various upstanding studs into successive verticalregister with the stud-tightening wrench 10 so that, upon descent of thelatter, the stud S will enter the socket 29 for stud-tighteningpurposes. It will be understood that the chuck 18 is continuouslyrotated and that, upon each descent thereof, the rotating wrench willoperatively engage the stud S to be tightened and effect the tighteningoperation automatically with no manipulative procedure on the part ofthe operator being required other than his manipulation of the usualdrill press lever (not shown) or other operating instrumentality such asa foot pedal or the like (also not shown).

Referring now to FIG. 2 the casing 12 embodies a circular top wall 26and a cylindrical side wall 28, and these walls together define thesocket 20. Slidably mounted and capable of limited rotational turningmovement in either direction within the socket 20 is a clutch actuatorin the form of a generally cylindrical slide member 30 which has formedtherein a stud-receiving socket 32. This last-mentioned socket is in theform of a bore 34 in the upper region of the slide member 30, and acounterbore 36 in the lower region of said slide member. The latterembodies a circular top wall 38 which defines the upper extremity or endof the bore 34. The juncture region between the bore 34 and thecounterbore 36 presents a downwardly projecting annular flange 39 havingformed therein a pair of diametrically opposite reaction slots 40 (seeFIG. 12), the function of which will be made clear presently.

Positioned loosely within the counterbore 36 of the socket 32 in theslide member 30 is an annular series of substantially radially disposedwedge plates 42, thirtysix such plates being illustrated herein forexemplary purposes although a greater or lesser number of such platesmay be employed if desired. As best illustrated in FIGS. 2 and 4 to 7,inclusive, each of these wedge plates is generally of wide area T-shapedesign, each plate having a wide T-shank 44 and a T-head 46. Two of thethirty-six wedge plates are of special design and they are designated bythe reference character 42a and are of slightly modified construction inthat they have somewhat wider T-shanks 44a than do the other thirtyfourwedge plates 42. The T-heads 46a of the two special wedge plates 42a arethe same in width as the T-heads 46 of the regular wedge plates 42.Preferably, the various wedge plates are in the form of metal stampingsin order to reduce the manufacturing cost of the wrench. An annularretainer ring 50 is threadedly received as at 52 in the rim region ofthe socket 32 and is provided with an upwardly extending circular boss54 and this defines a central opening 56 through the ring 50. Thevarious wedge plates 42 and 42a are arranged so that their T-headsextend vertically and their T-shanks inwardly. They are loosely held inposition within the socket 32 with the outer edges of their T-headsseated within an annular series of closely spaced, longitudinallyextending grooves 58 (see FIG. 10), such grooves being formed in thecounterbore 36 and there being one groove 58 for each wedge plate. Theupper and lower portions of the inner edges of the T-heads 46 and 46aare normally and respectively maintained in seated engagement orabutting relation with the outer peripheral surfaces of. the annulardepending flange 39 and the upwardly extending circular boss 54 by meansof a vertical series of elastorneric O-rings 60 which are positionednotches 61 in the central portions of the outer edges of the T-heads 46of the regular wedge plates 42 and notches 61a in the central portionsof the outer edges of the T-heads 46a of the two special wedge plates42a and function as garter-type springs to draw the various wedge plates42 and 42a radially inwardly with respect to the socket 32. The T-shanks44 and 44a of the wedge plates project radially inwards through theannular space which exists between the opposed rims of the annulardepending flange 39 and the upwardly extending circular boss 54 asclearly shown in FIG. 2, the radial extent of these T-shanks being butslightly greater than the radial thicknesses of said flange and boss.

As best illustrated in FIGS. 8 and 9, in the normally disengagedcondition of the multiple jaw clutch of the wrench 10, the various wedgeplates 42 and 42a do not extend in truly radial directions but, instead,they deviate slightly from true vertically extending, radial planes withthe inner end edges of the T-shanks 44 and 44a in substantialcontiguity. When a stud S which is to be tightened is projected into thesocket 32 through the central opening 56 in the retaining ring 50, theradial inclination Of the wedge plates is such that the inner end edgesof their T-shanks lie in close proximity to, but do not touch, the studas shown in FIG. 8. When the multiple jaw clutch of the wrench 10 isengaged upon the stud as shown in FIG. 9 by reason of a slightcounterclockwise rotation of the slide member 30 with respect to thecasing 14, the various wedge plates 42 and 42a assume substantiallyradial positions and the inner end edges of their T-heads securelyengage the stud S with a self-energizing action under the influence ofthe continous rotational movement of the power-actuated wrench as awhole, all in a manner that will become clear presently.

The aforementioned slight rotational movement of the slide member 30which is necessary to effect clutch engagement is automatically attainedby projection of the stud S into the socket 32, it being understood thatthis projection of the stud is a relative one which takes place when therotating wrench is lowered upon the fixed stud which projects upwardlyfrom the engine block 24.

Accordingly, the slide member 30, which, as previously pointed out,constitutes the clutch actuator for the wrench 10, is axially shiftablewithin the socket 20 in the body portion 14 of the casing 1-2 between alowered advanced position in which it is shown in full lines in FIG. 2and an upper or retracted position in which it is shown in dottedoutline in FIG. 2. Normally, the slide member 30 is maintained in itslowered advanced position by means of a helical compression spring 62which is disposed within the upper region of the socket 20 in the bodyportion of the wrench casing and beans at its upper end against thecircular top wall 26 and at its lower end against the top wall 38 of theslide member. Upon projection of a stud S into the socket 32, the upperend of the stud will engage said top wall 38 of the slide member 30 andas the rotating casing 12 continues to descend over the stud, theconsequent relative movement between the casing and the slide memberwill cause the latter to be moved to its retracted dotted line positionagainst the action of the spring 62.

The relative movement between the body portion 14 of the wrench casingand the slide member 30 just described is accompanied by a slightrotational movement of the slide member in a counterclockwise directionas viewed in FIGS. 8 and 9 under the influence of two shallow helicalcam grooves 70 (see FIG. 10) which are formed in the outer cylindricalsurface of the side wall of the slide member 30 and cooperaterespectively with a pair of diametrically opposite drive elements 72.The latter are carried by the casing body portion 14 and project intothe cam grooves.

Reference to FIGS. 3 and 10 will reveal the fact that the portion of theslide member side wall which surrounds the bore 34 is of appreciablethickness and that the portion of said side wall which surrounds thecounterbore 36 likewise is thick although of less thickness than thesaid first mentioned side wall portion. Both side wall portions are ofsufiicient thickness to accommodate the provision of the two shallowgrooves 70 at diametrically disposed regions of the slide member. Whilethese two grooves 70 have been referred to herein as being helicalgrooves, they are helical only in that the side edges 74 follow thecylindrical curvature of the cylindrical side wall in which they areformed. Due to the extremely long pitch of the involved helix, thebottoms 76 of these two grooves 70 may be made planar or flat withoutcutting through the slide wall of the slide member 30. The ends of thegrooves 70 are curved or rounded and establish the extent which theslide member is capable of sliding within the socket in the casing bodyportion 14, the upper ends 78 (see FIG. 10) of the cam grooves beingengageable with the drive elements 72 to limit the lowered advancedposition of the slide member and the lower ends 80 of the groovessimilarly limiting the upper retracted position of the slide member.These drive elements are loosely disposed in slots 82 (see FIGS. 2 and3) in the cylindrical side wall of the casing body portion 14 and theyproject radially inwardly of the slots, extend into the helical carngrooves 70 and ride on the flat bottoms 76 thereof. The drive elements72 are in the form of block-like structures having curved ends 84 andfiat sides 86, the former cooperating with the curved ends 78 and 80 ofthe helical cam grooves 70 to limit the stroke of the slide member 30,and the latter making camming contact with the side edges 74 of thegrooves 70 so that, upon relative sliding movement between the slidemember 30 and the casing body portion 14 between their two extremerelative positions, a slight angular turning movement of the slidemember within the casing 12 in opposite directions will take place. Thisturning movement of the slide member within the casing body portion 14is relied upon to effect clutch engagement and disengagement in a mannerthat will subsequently be set forth in detail. The two drive members 72are maintained in their operative positions within the slots 82 by meansof an encompassing retainer ring 90 which is held against longitudinalshifting movement on the casing body portion 14 by a rib 92 on the topside thereof and a split snap ring 94 on its bottom side.

Before entering into a description of the operation of the hereindescribed power wrench 10, it is deemed pertinent to set forth themanner in which the various parts of the wrench may be assembled at thefactory. Initially, the spring 62 is inserted from below into the upperend portion of the socket 20 and, thereafter, the slide member 30 isinstalled in said bore in its proper position wherein it directlyunderlies the spring. With the slide member 30 thus in place, thevarious wedge plates 42 and 42111 are individually slid into positionwith the outer side edges of the T-heads within the longitudinal grooves58 which, as heretofore stated, are formed in the counterbore 36.However, before the wedge plates are projected fully into position, thegarter-type O-rings 60 are installed in the notches 61 and 61a. When theO-rings have thus been installed, the entire series of radiallyextending wedge plates 42 and 42a is pushed fully into the counterbore36 of the socket 32 so that the upper end portions of the T heads 46 and46a encompass the downwardy projecting annular flange 39 and,thereafter, in order to complete the assembly of the wrench 10, theretainer ring 50 is screwed into position within the threaded portion 52of the rim region of the socket 32. During installation of the variouswedge plates 42 and 42a, it is essential that the two special wedgeplates 42a .be installed in the two diametrically disposed grooves 58which are in longitudinal register with the two reaction slots 40 to theend that when the series of wedge plates is finally pushed fully intothe counterbore 36 of the socket 32, the upper end portions of the wideT-shanks 44a (see FIG. 6 of the two special wedge plates) will enterthese slots and prevent circumferential shifting of said series of wedgeplates within the slide member 30. The present power wrench 10 is thuscapable of relative ease of assembly and, similarly, by a reversal ofthe assembly process just described, the wrench is easily dismantled forpurposes of inspection, replacement or repair of parts. Addition-ally,and as will be set forth presently, such dismantlement may readily beeffected for the purpose of substitution of a special slide member suchas that which is illustrated in FIG. 12 at and by means of which thewrench may be converted to use as a stud removal wrench.

In the operation of the power wrench 10 for stud-tightening purposes,the engine block 24 will be mounted on a suitable indexing table whichis capable of being shifted so as successively to bring the variousstuds S into vertical alignment with the chuck-supported rotating wrench10. As soon as this alignment has been attained, the rotating wrench islowered upon the subjacent stud so that the upper threaded end of thestud passes through the central opening 56 of the retainer ring 50,enters the socket 32 and engages the top wall 38 of the slide member 30.Engagement of the stud S with the top Wall 38 will arrest furtherdownward movement of the slide member 30* while the rotating wrenchcasing 12 continues to descend. During such descent, the helicalcompression spring 62 will become compressed as the upper end of theslide member 30 moves deeper into the socket 20. The relative slidingmovement thus established between the slide member 30 and the bodyportion 14 of the casing 12 will cause the two drive elements 72 totraverse the longitudinal extent of the shallow helical grooves 70, andin so traversing the grooves, a slight turning movement of the slidemember 30 within the surrounding casing body portion 14 will take placein a counterclockwise direction as viewed in FIG. 8.

The axial distance between the top Wall 38 of the slide member 30 andthe various wedge plates 42 and 42a is such that, at the time the upperend of the stud S engages said top Wall, the T-shanks 44 and 44a of thewedge plates will be in radial register with the smooth unthreadedportion of the stud S. Not only will such radial register obtain,

but additionally, the radial extent of the wedge plates and thedimensions of the other associated elements of the wrench are sodesigned that at the time the stud S initially enters the socket 32, theinner edges of the T-shanks 42 and 42a will frictionally engage the studS .as shown in FIG. 8, thus slightly displacing all of the wedge platesradially outwardly so that the garter O-rings 60 maintain them infrictional engagement with the stud. The two slots 40 (see FIG. 11) areprovided for the purpose of preventing collapse of the entire annularseries of wedge plates so that the inner edges of the T-shanks 44 and4411 which are disposed in substantial contiguity in a circumferentialdirection will be at all times maintained in such contiguity.

As soon as the aforementioned relative turning movement of the slidemember 30 and the body portion 14 of the casing 12 takes place, thevarious longitudinal grooves 58 in the counterbore 36 tend to impart acollective counterclockwise shifting movement of the outer edges of theT-heads 46 and 46a of all of the wedge plates, while the inner edges ofthe T-shanks 44 and 44a are frictionally restrained. In this manner, aself-energizing action of all of the Wedge plates takes place tending tostraighten them out into a radial position, thus exerting a powerfulbinding action on the stud S by the rotating wrench 10. The stud S isthus firmly engaged by the multiple clutch jaws which are formed by thewedge members and it is rotated in a stud-tightening direction.

As soon as the stud S has been thus driven into the socket 22 (seeFIG. 1) in the engine block 24 to the desired depth as evidenced by thereading of a depth gauge in associated relation with the drill pressstand, continued lowering of the Wrench will be terminated and thewrench will then be immediately raised, During such raising of thewrench, the spring 62 will maintain the top wall 38 of the slide member30 in contact with the upper end of the stud S while the rotating casing12 will move upwardly with respect to the slide member 30. The neteflfect of this relative motion between the slide member and the casingof the wrench will be to effect reverse relative rotation between theslide member 30 and the casing 12 as the two drive elements 72 againtraverse the shallow helical grooves 70, thus tilting the various wedgeplates 42 and 42a away from their generally radial positions andreleasing the stud S. It is to be noted at this point that the width ofthe two slots 40 (see FIG. 11) is slightly greater than the thickness ofthe wedge plates 42a so that freedom of tilting movement of thesespecial wedge plates is not hindered.

As soon as the drill press chuck and the wrench have been restored totheir uppermost position, the work supporting table which supports theengine block 24 may be indexed to bring a successive stud S to betightened into position beneath the wrench for the next succeedingstudtightening operation.

The present stud-tightening wrench assembly is capable of being employedfor stud removal purposes by the simple expedient of substituting forthe slide member the different slide member 130 of FIG. 11. Said slidemember 130 remains substantially the same as the slide member 30 exceptfor the fact that the two shallow helical cam grooves 170 that areformed in the cylindrical side wall of said slide member 130 extend in areverse direction. In view of the similarity between the two slidemembers 30 and 130, and in order to avoid needless repetition ofdescription, similar characters of reference but of a higher order havebeen applied to the corresponding parts of the slide member 130 asbetween the disclosures of FIGS. 10 and 12. It will be understood thatwhen the slide member 130 has been substituted for the slide member 30,the wrench 10 embodying the slide member 130 will be rotated in areverse stud removal direction. Thus, upon descent of the wrench andconsequent projection of the upper end of the stud S into the socket 32,substantially the same clutch engagement phenomena will take place andthe stud S will be gripped firmly by the inner edges of the T-shanks 44and 44a of the wedge plates 42 and 42a due to the self-energizing actionof these plates, but because the wrench is rotating in the reversedirection, the stud S will be rotated in a direction tending to unthreadthe same from the socket 22 in the engine block 24. Stud removaloperations are not a frequent occurrence, either in assembly linepractice or in a maintenance or repair shop. Thus, for economy reasons,it may be found expedient for the owner of one of the present powerstudtightening wrenches to keep on hand one of the slide mem bers and toeffect the necessary substitution when an occasional stud-removaloperation is required. However, where stud-removal operations are morefrequently encountered, it may be expedient for wrench owner to maintaintwo of the wrenches, one embodying the slide member 30 and the otherembodying the slide member 130.

The invention is not to be limited to the exact arrangement of partsshown in the accompanying drawings or described in this specification asvarious changes in the details of construction may be resorted towithout departing from the spirit or scope of the invention. Therefore,only insofar as the invention is particularly pointed out in theaccompanying claims is the same to be limited.

Having thus described the invention what I claim as new and desire tosecure by Letters Patent is:

1. A power stud-tightening wrench comprising a vertically extending,generally cylindrical casing embodying means at its upper end forconnecting it to a continuously rotating chuck, and having extendingaxially inwardly from its lower end a socket into which a stud isadapted to be projected endwise, a generally tubular stud-em circlingslide member coaxial with and axially slidable in said socket betweenupper and lower positions, means yieldingly biasing said slide membertoward its lower position, said slide member being capable of limitedturning movement within the socket bodily between first and secondangular positions, interengaging cam means on said casing and slidemember and effective during movement of the slide member between itslower and upper positions to effect turning movement of the slide memberbetween its first and second angular positions, a series ofsubstantially radially disposed wedge plates loosely mounted within saidtubular slide member, having outer edges bearing against the inner wallof said slide member and having their inner edges disposed in closeproximity to each other and designed for frictional engagement with astud which has been projected into said socket, means wieldinglymaintaining said wedge plates slightly displaced from truly radialpositions so that upon relative turning movement of the slide memberwith respect to the casing from its first angular positiOn to its secondangular position a self-energizing wedging action of the plates betweenthe Wall of the casing and the stud will take place, and a shoulderformed internally of the slide member and engageable with the end of astud during projection thereof into said socket for moving the slidemember toward its upper axial position against the action of saidyieldable biasing means.

2. A power stud-tightening wrench as set forth in claim 1 and whereinsaid interengaging cam means comprises a series of elongated helicalgrooves in the slide mmeber and a series of cooperating guide elementscarried by the casing and projecting into said grooves.

3. A power stud-tightening wrench as set forth in claim 2 and whereinsaid helical grooves are two in number and are substantiallydiametrically disposed on opposite sides of the slide member.

4. A power stud-tightening wrench as set forth in claim 1 and whereinsaid biasing means comprises a compression spring interposed between thetop wall of said socket in the casing and the top wall of the slidemember.

5. A power stud-tightening wrench as set forth in claim 3 and whereinthe opposite ends of said helical grooves are engageable with said guideelements to determine the upper and lower positions of the slide member.

6. A power stud-tightening wrench as set forth in claim 1 and whereinthe inner surface of the side wall of the slide member is provided withan annular series of longitudinally extending grooves, one for eachwedge member, and in which grooves the outer edges of the wedge membersare seated.

7. A power stud-tightening wrench as set forth in claim 1, wherein saidslide member is provided with an axial bore and an enlarged counterbore,the juncture region between said bore and counterbore being formed witha depending annular flange, and wherein each wedge plate is generally ofT-shape construction and includes a T-head and a T-shank, the upper endportion of the T-head of each wedge plate projecting into the annulusexisting between said annular flange and the wall 01 said counterbore,the lower end of said counterbore being internally threaded said wrenchincluding, additionally, a retaining ring threadedly received in thethreaded lower 10 end of the counterbore, said retaining ring beingformed with a centrally disposed annular boss, the lower end portion ofthe T-head of each wedge plate projecting into the annulus existingbetween said annular boss and the wall of said counterbore.

References Cited UNITED STATES PATENTS MYRON C. KRUSE, Primary Examiner.

US. Cl. X.R.

